Direct coupled coaxial line amplifier



Oct. 20, 1964 T. s. WEAVER 3,153,765

DIRECT COUPLED COAXIAL LINE AMPLIFIER Filed oct. 4, 1962 Q *Q INVENTOR 7am/ffy J. WMI/ef BY s fff. ,M s

United States Patent O 3,153,765 DERECT COUPLED CGAXIAL LINE AMPLIFIER Tommy S. Weaver, Arnold, Md., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed (ict. 4, 1962, Ser. No. 223,504 1 Claim. (Cl. 339-56) The present invention relates to a coaxial line amplifier and more particularly to an amplier that is direct coupled into a coaxial line.

Heretofore, direct coupling into a coaxial line amplifier has seldom been used as it has been difficult to separate the D C. and the R.F. energy. In U.S. Patent 2,579,820, Ultrahigh-Frequency System Employing Neutralizing Probes, issued C. E. Haller et al, on December 25, 1951, there is shown one heretofore used method of coupling an amplier in a coaxial transmission line wherein a pair of neutralizing probes are provided for neutralizing the energy fed through the vacuum tube due to the anodecathode interelectrode capacitance. The neutralization provided by the probes reduces the regeneration due to the interelectrode capacitance to a point or value below that necessary for oscillation.

In another type of coupling, as shown in U.S. Patent 2,643,302, Electron Discharge Device and Circuits for Neutralized Coaxial Line Amplifiers, issued E. M. Bradburd on June 23, 1953, the vacuum tube amplifier is incorporated in a coaxial line type `of amplifier comprising an outer cylindrical conductor shell to which the anode of the tube is capacitively coupled and which may be considered as being at ground potential.

In the present invention, low impedance coaxial lines are used as the center conductors of a coaxial amplifier for the purpose of allowing direct coupling to the input and output lines. Direct coupling has advantage over loop or probe coupling in that the center conductor is actually grounded at the end of the cavity rather than being bypassed by a capacitor and thus a perfect match is more easily achieved.

It is a general object of the present invention to provide an improved means of coupling an amplifier in a coaxial line.

Another object of the present invention is to provide means for direct coupling an amplifier in a coaxial line.

Still another object of the present invention is to provide a means for direct coupling into an amplifier and for separating the D.C. and RF. energy.

Other objects and advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing which is a diagram, partly in section, showing a preferred embodiment of the present invention.

Referring now to the drawing, there is shown a pair of hollow cylinders 11 and 12 that are abutted end to end and held together by screws 13 that are positioned in flanges 14 and 15. Cylinder 11 is provided with an outer shell 16, and an inner shell 17 that is concentric with the outer shell 16. Cylinder 12 is provided with an outer shell 18, and end plates 21 and 22 are provided on cylinders 11 and 12, respectively.

An amplifier tube 23, which by way of example might be a JAN-7077 tube, is positioned by the abutting end plates 24 and 25. There is shown in the drawing a JAN-7077 tube which has an anode 31, grid 32, cathode 33, heater 34, and insulators 35 through 37. In the plate cavity 41, the center conductor of the quarter-wave coaxial cavity is a coaxial line in itself. One end of an inner conductor 42 contacts the anode 31 and the other 3,153,765 Patented Oct. 20, 1964 end of inner conductor 42 connects to a decoupling network and to a voltage source (B+). An outer conductor 43 is concentrically positioned around inner conductor 42 and electrically insulated therefrom by insulator 44, which by way of example might be a thin layer of insulating tape. An output connector 45 is provided on the plate cavity end and comprises an outer connector 46 which is attached to outer shell 18 and an inner connector 47 which is connected to outer conductor 43.

Considering RF. energy only, the center conductor in the plate cavity 41 is made up of the outer conductor 43 to point A, and then the impedance between the outer conductor 43 and the inner conductor 42, and then the length of the inner conductor 42 to the anode 31 of tube 23. The impedance between the anode 31 and point A is in series with the plate resistance of the amplifier tube 23 and must be kept at a relatively low value. By way of example, when a JAN-7077 tube is used, the plate resistance is approximately 2000 ohms and the maximum allowable impedance at point A would be about 20 ohms.

Referring now to the cathode cavity 51, an inner conductor 52 is concentrically positioned within the inner shell 17 and electrically isolated therefrom by isolator 53, which by way of example might be a thin layer of insulating tape. One end of conductor 52 is connected to the cathode 33 of amplifier tube 23 by means of a jumper 54. The inner conductor 52 is provided with a hole 54 through which heater leads 55 can be passed and then connected to a suitable source of Voltage. An input connector 56 is provided on the cathode cavity end and comprises an outer connector 57 which is attached to the outer shell 16 and an inner connector 58 which is connected to the inner shell 17.

It can thus be seen from the above description that the objects of the invention have been achieved by providing a relatively simple device for direct coupling an amplifier in a coaxial line.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood, that within the scope of the appended claim, the invention may be practiced otherwise than as specifically described.

What is claimed is:

An amplifier of the coaxial line type comprising:

an electron tube having cathode, anode, grid, and

heater electrodes,

a first hollow cylinder having concentric outer and inner shells and having end plates thereon each having a relatively small aperture therein,

a second hollow cylinder having end plates thereon each having a relatively small aperture therein, one said end plate of said second hollow cylinder abutting one -said end plate of said first hollow cylinder and clamping said grid electrode whereby said cathode electrode of said electron tube extends through said aperture of said end plate into said first hollow cylinder and said anode electrode of said electron tube extends through said aperture of said end plate into said second hollow cylinder,

a hollow cathode lead connected to said cathode electrode and concentrically mounted within said inner shell, said cathode lead being insulated from said inner shell thereby providing a coaxial line,

a coaxial line mounted within said second hollow cylinder having an inner conductor connected to said anode electrode and an outer conductor having one end connected to said end plate opposite said end plate abutting said end plate of said first hollow cylinder,

3,153,765 3 4- a coaxial input connector having an outer conductor References Cited in the file of this patent connected to said outer shell and an inner conduc- UNITED STATES PATENTS tor connected to sald inner shell, and

a coaxial output connector having an outer conductor 2,435,585 Iaftm'fm Fell 10, 1948 connected to said second hollow cylinder and an 5 2,523,307 aldlal Sept-26, 1950 inner conductor connected to said outer conductor 2,542,974 AbbO et al. Feb. 27, 1951 Vof said `coaxial line mounted Within said second 2,631,953 Bladburd June 22, 1954 hollow cylinder, 2,759,101 Canddl et al Aug. 14, 1956 

